Preheat your oven to 350 degrees F and cut out 2 circles of parchment to fit into 2 8-inch cake pans (I used 9-inch), then butter well or spray with non-stick spray. Whisk together your cake flour (or homemade cake flour), all-purpose flour, baking powder and salt. Set it aside.

In the bowl of your mixer, beat together the butter and sugar until fluffy, scraping down the sides of the bowl as needed, for no less than 3 minutes. Add in the egg whites, one at a time, incorporating the first before adding the next, again, scraping down the sides of the bowl as necessary. Add in the oil and the vanilla and mix to combine.

Add the flour and milk into the batter in alternating batches, starting and ending with the flour (so add ⅓ of the flour, ½ of the milk, ⅓ of the flour, the rest of the milk, and then the rest of the flour), scraping down the sides of the bowl as needed. Fold in the sprinkles - resist the urge to add more than the recommended ⅔ cup, as I promise they will be plenty!

Divide your batter evenly into your two prepared pans. Sprinkle the remaining 1 tablespoon of sprinkles over each of the cakes. Bake for 25-30 minutes, until lightly golden and set. Allow the cakes to cool completely before running a knife around the edge of the cakes and removing them from the pans to frost.

When the cakes are ready to frost, make your frosting by beating together your butter and sugar until smooth, then adding in the vanilla and salt and beating for another few minutes.

To frost your cake, place one of your cakes on a secure work surface (I like to put a dollop of frosting under a cardboard cake board to keep it still). Place a dollop of about ⅓ of your frosting on top of your first layer and smooth it out.

Place your next take on top, top side down so that the flat side is facing up, and push the layers together a bit to secure them. Frost your cake with a thin layer, called a crumb layer, just to secure any loose crumbs. Place your cake in the fridge for 20-30 minutes to secure the crumb layer. Finish frosting your cake as you like, then finish with lots of sprinkles and/or edible glitter, depending on how crazy you want to get. Let the cake chill in the fridge for another 30 minutes or so before slicing and serving. This cake will keep well in an airtight cake container in the refrigerator for up to 3 days.